RxJS vs Promises

In a nutshell, the main differences between the Promise and the Observable are as follows:

• The Promise is eager, whereas the Observable is lazy,
• The Promise is always asynchronous, while the Observable can be either asynchronous or synchronous,
• The Promise can provide a single value, whereas the Observable is a stream of values (from 0 to multiple values), you can apply RxJS operators to the Observable to get a new tailored stream.